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BQ25606: BQ25606 charging fault problem consultation

Part Number: BQ25606

The hardware system is in the charging state, VSYS is loaded, and VBAT is also loaded. It has been charging for less than 20 hours, and it is found that the battery is under voltage protection. The customer schematic diagram is as follows

My analysis here may enter the safe timer state, and exit the charging mode after 20 hours. However, according to the manual, the voltage drops to VRECHG will enter a new charging cycle, and the Safe timer will be reset at the same time.
Please help us to look at the problem, thanks.

  • Hello Alon,

    If you have a external load on VSYS then the charger may be in supplement mode and drain the battery to low voltage protection.

    We would need more information of the system to debug further: SYS load, voltage and current log during this period, VBUS current and voltage.

    Sincerely,

    Wyatt Keller

  • Hi Wyatt,
    thank you for your reply.
    During charging, a battery with VBAT=3.7V is connected to the system and starts charging VBUS=5.1V IBUS=1.2A (constant current);
    When it is almost full, the current begins to drop (constant voltage), until Vin=100mA or so, the current does not fluctuate .During this period ISYS=200mA IBAT=300mA Load power consumption is fixed

    Add new questions
    Question A:
    1. After the battery is fully charged, as the battery voltage drops and reaches the VRECHG threshold, will a new charging cycle be automatically started? Will the chip automatically detect the battery voltage?
    2. If it can be detected that a new charging cycle is started, what is the charging status at this time? Constant pressure? Or constant current?
    3. If it is a constant voltage, can the charging current regulation meet the power supply of the VBAT post-stage? If it can't be satisfied, what will happen?
    Question B:
    Charging Safety Timer


    1. When did this safety timer start to run?
    Does it work when charging is turned on? When the monitoring battery voltage is lower than VBATLOWV for 2h, the charging cycle is closed, and when the monitoring battery voltage is higher than VBATLOWV for 10h, the charging cycle is closed?
    2. The normal charging cannot exceed 20h? Does the charging stop when the timer overflows?

  • Add a new question C: When the charging is almost full, is the charger constant voltage charging or cross-current charging, if it is constant voltage, what is the current? If the current is too small, it will not be able to supply the load, and the battery will also consume power. Please help answer, thanks

  • Hi,

    1.Referring to 8.3.6.1 Autonomous Charging Cycle on the d/s, When a fully charged battery is discharged below recharge threshold , the device automatically starts a new charging cycle.

    2. The safety timer is 2 hours when the battery is below VBATLOWV threshold and 10 hours when the battery is higher than VBATLOWV threshold.

    Thanks,

    Ning.

  • So can't it be charged continuously for more than 20 hours?

    Thanks,

    Alon Chen.

  • Alon,

    The device has built-in safety timer to prevent extended charging cycle due to abnormal battery conditions.

    8.3.6.6 Charging Safety Timer on the d/s, During input voltage, current, JEITA cool or thermal regulation, the safety timer counts at half clock rate as the actual charge current is likely to be below the register setting. For example, if the charger is in input current regulation throughout the whole charging cycle, the safety timer will expire in 20 hours. In normal charging operation without input voltage, current, JEITA cool or thermal regulation, the safety timer should expire within 20 hours.

    Thanks,

    Ning.